A series of grazing (chapters 2, 3, 5 and 6) in-vitro (chapter 4) and modelling trials (chapters ... more A series of grazing (chapters 2, 3, 5 and 6) in-vitro (chapter 4) and modelling trials (chapters 1 and 7) were combined with the following objectives: a) to gain insight in the main mechanisms controlling dry matter intake (DMI), intake rate (IR) and grazing time (GT), during the first grazing session after a.m. milking, b) to judge the relative importance of rumen fill and the concentration of fermentation products in the rumen liquor as candidates to signal the end of the grazing sessions and c) to develop new and modify and evaluate existing simulation model, to operate under non-steady state conditions with the aim to predict DMI, rumen fermentation and supply of nutrients.Increasing the length of the allowed grazing time significantly increased DMI (P<0.01), the proportion of time spent actively eating (P<0.01) and DM rumen pool size after grazing (P<0.05). The allowed grazing time did not have any significant effect on total and liquid rumen pool sizes after grazing b...
ABSTRACT Five multiparous lactating Holstein-Friesian dairy cows fitted with rumen cannula were a... more ABSTRACT Five multiparous lactating Holstein-Friesian dairy cows fitted with rumen cannula were allowed to graze perennial ryegrass swards. Next to a control treatment of grazing only, pelleted barley (PB), pelleted maize (PM), toasted and subsequently pelleted barley (TPB), and toasted and subsequently pelleted maize (TPM) were fed as a supplement in two equal portions. Before and after 3 h of grazing the rumen content was evacuated, weighed, sampled and returned to the animals. Then the cows were kept inside the barn and starved for 6 h, after which rumen evacuations were repeated. The estimated clearance rates of starch showed significant differences (P&lt;0.001) between grain types and compared to unsupplemented animals the apparent mminal clearance of nitrogen was significantly (P&lt;0.001) reduced. Supplementation with processed grains significantly increased (P&lt;0.05) the milk production and significantly (P&lt;0.001) decreased milk fat percentage. It is concluded that supplementing grass with high-energy low protein feeds, such as grains, substantially improves the N utilization and reduces the urea output in milk.
ABSTRACT Abstract Text: Primiparous Holstein dairy cows (n = 44, 595 ± 41 kg of BW, 3.7 ± 0.3 of ... more ABSTRACT Abstract Text: Primiparous Holstein dairy cows (n = 44, 595 ± 41 kg of BW, 3.7 ± 0.3 of BCS) were used in a randomized block design to study the effect of different herbage allowances on endometrial gene expression at day 7 of the estrous cycle. Cows were assigned to three grazing treatments (TREAT; n=11 each): high (HA, 30 kgDM/cow/d), medium (MA, 15 kgDM/cow/d) and low (LA, 7.5 kgDM/cow/d) herbage allowance (mixed pasture, 2600 kgDM/ha) or to a total mixed ratio (55% forage, 45% concentrate) fed ad-libitum (TMR) from calving to 56 days postpartum (DPP). At 57 DPP, estrous cycles were synchronized (intravaginal progesterone insert and PGF2alpha injection) and estrus was detected twice a day. At day 7 of the estrous cycle uterine biopsies were obtained to measure mRNA expression of insulin, leptin and adiponectin receptors (INSR, LEPR-long isoform, ADIPOR1 and ADIPOR2, respectively) by SYBR-Green real time RT-PCR. Data were normalized to the expression of three internal control genes and analyzed in a mixed model using TREAT and occurrence of ovulation (yes/no) as fixed effects and block as a random effect. All cows mobilized BCS after calving (0.5 units for TMR and HA and 1 unit for MA and LA cows). Ovulation rate after synchronization (55%) did not differ among treatments. Endometrial expression of INSR, LEPR-long and ADIPOR1 mRNA were not different between treatments. However, ADIPOR2 mRNA expression, which was 2 to 15-fold more abundant than ADIPOR1 mRNA, was affected by TREAT (P&lt;0.01). Endometrial ADIPOR2 mRNA was the greatest in TMR, the lowest in HA and MA, and intermediate in LA cows (1.0a, 0.3b, 0.2b, 0.7ab± 0.02, respectively). In addition, INSR mRNA had a 2-fold and ADIPOR2 mRNA had a 5-fold decrease (P&lt;0.03) in ovulated than non-ovulated cows. We have not found reports of adiponectin receptors in the ruminant uterus, but in other species it has been implicated in endometrial changes in preparation to embryo implantation and reduced ADIPOR2 mRNA has been associated with decreased uterine receptivity. Interestingly, both INSR and ADIPOR2 were downregulated suggesting the interdependence of these two factors as has been suggested for insulin/adiponectin. Thus, taking into account that adiponectin is a metabolic signal, these results suggest a direct role of this hormone in uterus moderating the success of pregnancy and ADIPOR2 mRNA could be, among others, one of the molecules linking a better nutrition and metabolic status with reduced embryo mortality. Keywords: nutrition, reproduction, dairy cows
Abstract Text: Multiparous cows (n=25) were used in a randomized complete block design to study t... more Abstract Text: Multiparous cows (n=25) were used in a randomized complete block design to study the effects of nutrition during the first 60 d postpartum (DPP) on hepatic expression of genes associated with fatty acid oxidation. Cows were assigned to 3 treatments (TREAT): TMR= total mixed ration (30 kg DM/d offered; 45% forage, 55% concentrate); G1= 50% pasture in one (am) grazing session (6 h; pasture allowance =15 kg DM/d) + 50% TMR (15 kg DM/d offered) and G2= 50% pasture in two (am/pm) grazing sessions (9 h; pasture allowance =15 kg DM/d) + 50% TMR (15 kg DM/d offered). Liver biopsies were collected at -40, -20, +10 and +55 DPP to measure the abundance of mRNA of pyruvate dehydrogenase (PDH1A) and pyruvate dehydrogenase kinase (PDK), acyl-CoA dehydrogenase, very long chain (ACADVL), acyl-CoA oxidase (ACoAoX), carnitine palmitoyltransferase-1A (CPT1A), β- hydroxy-β-methylglutaryl-coenzyme A (HMGCOA) and citrate synthase (CS) by SYBR-Green real time RT-PCR. Data were analyzed in a...
Introduction Animal intake and behavior under grazing conditions are affected by sward characteri... more Introduction Animal intake and behavior under grazing conditions are affected by sward characteristics. In dairy cows, Gibb et al., (1997), found a direct effect of pasture height on bite mass. When sward height decreases, animal response is to increase grazing time and bite rate, but this compensation may not be enough in short swards, affecting milk production. Penning et al., (1991), working with sheep, concluded that height can be used as an intake and production control, due to sward structure developed by grazing management. The aim of this study was to evaluate the effect of grazing intensity on grazing behavior, intake and milk production of Holstein cows grazing perennial pasture, with Festuca arundinacea as the main component. Materials and Methods The experiment took place between 18/10 and 16/11, 2008, at Estación Experimental M. A. Cassinoni, Facultad de Agronomía, Paysandu, Uruguay (32 º 22'S -58 ° 03'W). Treatments were three grazing intensities 4, 7 and 10 cm...
A series of grazing (chapters 2, 3, 5 and 6) in-vitro (chapter 4) and modelling trials (chapters ... more A series of grazing (chapters 2, 3, 5 and 6) in-vitro (chapter 4) and modelling trials (chapters 1 and 7) were combined with the following objectives: a) to gain insight in the main mechanisms controlling dry matter intake (DMI), intake rate (IR) and grazing time (GT), during the first grazing session after a.m. milking, b) to judge the relative importance of rumen fill and the concentration of fermentation products in the rumen liquor as candidates to signal the end of the grazing sessions and c) to develop new and modify and evaluate existing simulation model, to operate under non-steady state conditions with the aim to predict DMI, rumen fermentation and supply of nutrients.Increasing the length of the allowed grazing time significantly increased DMI (P<0.01), the proportion of time spent actively eating (P<0.01) and DM rumen pool size after grazing (P<0.05). The allowed grazing time did not have any significant effect on total and liquid rumen pool sizes after grazing b...
ABSTRACT Five multiparous lactating Holstein-Friesian dairy cows fitted with rumen cannula were a... more ABSTRACT Five multiparous lactating Holstein-Friesian dairy cows fitted with rumen cannula were allowed to graze perennial ryegrass swards. Next to a control treatment of grazing only, pelleted barley (PB), pelleted maize (PM), toasted and subsequently pelleted barley (TPB), and toasted and subsequently pelleted maize (TPM) were fed as a supplement in two equal portions. Before and after 3 h of grazing the rumen content was evacuated, weighed, sampled and returned to the animals. Then the cows were kept inside the barn and starved for 6 h, after which rumen evacuations were repeated. The estimated clearance rates of starch showed significant differences (P&lt;0.001) between grain types and compared to unsupplemented animals the apparent mminal clearance of nitrogen was significantly (P&lt;0.001) reduced. Supplementation with processed grains significantly increased (P&lt;0.05) the milk production and significantly (P&lt;0.001) decreased milk fat percentage. It is concluded that supplementing grass with high-energy low protein feeds, such as grains, substantially improves the N utilization and reduces the urea output in milk.
ABSTRACT Abstract Text: Primiparous Holstein dairy cows (n = 44, 595 ± 41 kg of BW, 3.7 ± 0.3 of ... more ABSTRACT Abstract Text: Primiparous Holstein dairy cows (n = 44, 595 ± 41 kg of BW, 3.7 ± 0.3 of BCS) were used in a randomized block design to study the effect of different herbage allowances on endometrial gene expression at day 7 of the estrous cycle. Cows were assigned to three grazing treatments (TREAT; n=11 each): high (HA, 30 kgDM/cow/d), medium (MA, 15 kgDM/cow/d) and low (LA, 7.5 kgDM/cow/d) herbage allowance (mixed pasture, 2600 kgDM/ha) or to a total mixed ratio (55% forage, 45% concentrate) fed ad-libitum (TMR) from calving to 56 days postpartum (DPP). At 57 DPP, estrous cycles were synchronized (intravaginal progesterone insert and PGF2alpha injection) and estrus was detected twice a day. At day 7 of the estrous cycle uterine biopsies were obtained to measure mRNA expression of insulin, leptin and adiponectin receptors (INSR, LEPR-long isoform, ADIPOR1 and ADIPOR2, respectively) by SYBR-Green real time RT-PCR. Data were normalized to the expression of three internal control genes and analyzed in a mixed model using TREAT and occurrence of ovulation (yes/no) as fixed effects and block as a random effect. All cows mobilized BCS after calving (0.5 units for TMR and HA and 1 unit for MA and LA cows). Ovulation rate after synchronization (55%) did not differ among treatments. Endometrial expression of INSR, LEPR-long and ADIPOR1 mRNA were not different between treatments. However, ADIPOR2 mRNA expression, which was 2 to 15-fold more abundant than ADIPOR1 mRNA, was affected by TREAT (P&lt;0.01). Endometrial ADIPOR2 mRNA was the greatest in TMR, the lowest in HA and MA, and intermediate in LA cows (1.0a, 0.3b, 0.2b, 0.7ab± 0.02, respectively). In addition, INSR mRNA had a 2-fold and ADIPOR2 mRNA had a 5-fold decrease (P&lt;0.03) in ovulated than non-ovulated cows. We have not found reports of adiponectin receptors in the ruminant uterus, but in other species it has been implicated in endometrial changes in preparation to embryo implantation and reduced ADIPOR2 mRNA has been associated with decreased uterine receptivity. Interestingly, both INSR and ADIPOR2 were downregulated suggesting the interdependence of these two factors as has been suggested for insulin/adiponectin. Thus, taking into account that adiponectin is a metabolic signal, these results suggest a direct role of this hormone in uterus moderating the success of pregnancy and ADIPOR2 mRNA could be, among others, one of the molecules linking a better nutrition and metabolic status with reduced embryo mortality. Keywords: nutrition, reproduction, dairy cows
Abstract Text: Multiparous cows (n=25) were used in a randomized complete block design to study t... more Abstract Text: Multiparous cows (n=25) were used in a randomized complete block design to study the effects of nutrition during the first 60 d postpartum (DPP) on hepatic expression of genes associated with fatty acid oxidation. Cows were assigned to 3 treatments (TREAT): TMR= total mixed ration (30 kg DM/d offered; 45% forage, 55% concentrate); G1= 50% pasture in one (am) grazing session (6 h; pasture allowance =15 kg DM/d) + 50% TMR (15 kg DM/d offered) and G2= 50% pasture in two (am/pm) grazing sessions (9 h; pasture allowance =15 kg DM/d) + 50% TMR (15 kg DM/d offered). Liver biopsies were collected at -40, -20, +10 and +55 DPP to measure the abundance of mRNA of pyruvate dehydrogenase (PDH1A) and pyruvate dehydrogenase kinase (PDK), acyl-CoA dehydrogenase, very long chain (ACADVL), acyl-CoA oxidase (ACoAoX), carnitine palmitoyltransferase-1A (CPT1A), β- hydroxy-β-methylglutaryl-coenzyme A (HMGCOA) and citrate synthase (CS) by SYBR-Green real time RT-PCR. Data were analyzed in a...
Introduction Animal intake and behavior under grazing conditions are affected by sward characteri... more Introduction Animal intake and behavior under grazing conditions are affected by sward characteristics. In dairy cows, Gibb et al., (1997), found a direct effect of pasture height on bite mass. When sward height decreases, animal response is to increase grazing time and bite rate, but this compensation may not be enough in short swards, affecting milk production. Penning et al., (1991), working with sheep, concluded that height can be used as an intake and production control, due to sward structure developed by grazing management. The aim of this study was to evaluate the effect of grazing intensity on grazing behavior, intake and milk production of Holstein cows grazing perennial pasture, with Festuca arundinacea as the main component. Materials and Methods The experiment took place between 18/10 and 16/11, 2008, at Estación Experimental M. A. Cassinoni, Facultad de Agronomía, Paysandu, Uruguay (32 º 22'S -58 ° 03'W). Treatments were three grazing intensities 4, 7 and 10 cm...
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